1. Field of the invention
The present invention relates to an equalizing apparatus in a single carrier system, and more particularly to an equalizing method and apparatus which can improve equalization performance in dynamic channel circumstances.
2. Description of the Prior Art
As generally known in the art, linear equalizers or decision feedback equalizers are used as equalizing apparatuses in a single carrier system.
FIG. 1 is a schematic block diagram regarding a linear equalizer 10. A linear equalizer 10 includes a filter unit 11 having a FIR-type filter and a switching unit 15 for operating selectively according to an operation mode of the equalizer. Equalization is performed by repeating a process which obtains an equalization error value corresponding to the operation mode selected by the switching unit 15 and updates coefficients of all filter taps.
When the operation mode is a blind mode, an error calculating unit 17 calculates the equalization error value using an output signal of the filter unit 11 and an output signal of a level decision unit 16 selected by the switching unit 15. Also, when the operation mode is a training mode, the error calculating unit 17 calculates the equalization error value using the output signal of the filter unit 11 and a field sync signal selected by the switching unit 15.
As described above, the equalization error values obtained from each of the operation modes are inputted to the filter unit 11. The filter unit 11 updates coefficients of all the filter taps using the inputted equalization error values. Accordingly, multi-path of a received signal is removed.
FIG. 2 is a schematic block diagram regarding a decision feedback equalizer 20. The decision feedback equalizer 20 includes a FF (feed forward) section 21 having a FIR-type filter for removing a pre-ghost and post-ghost of a received signal, a FB (feed back) unit 23 having a IIR-type filter for removing a post-ghost of the received signal and a switching unit 25 for operating selectively according to an operation mode of the equalizer 20, which is either a blind mode or a training mode. An equalization is performed by obtaining an equalization error value corresponding to an operation mode selected by the switching unit 25 and updating each coefficient of a filter tap of the FF unit 21 and the FB unit 23.
When the operation mode is a blind mode, an error calculating unit 27 calculates the equalization error value using an output signal of an adder 22 adding output signals of the FF unit 21 and the FB unit 23 and an output signal of a level decision unit 26 selected by the switching unit 25.
Also, when the operation mode is a training mode, the error calculating unit 27 calculates the equalization error value using the output signal of the adder 22 adding the output signals of the FF unit 21 and the FB unit 23 and a field sync signal selected by the switching unit 25.
As described above, the equalization error values obtained from each of the operation modes are inputted to the FF unit 21 and the FB unit 23, respectively. The FF unit 21 and the FB unit 23 update coefficients of all the filter taps using the inputted equalization error values. Accordingly, multi-path of a received signal is removed.
The equalization process of a conventional equalizer described above compensates for the channel distortion of the received signal by updating over and over coefficients of all the filter taps of the FF unit and the FB unit on the basis of the equalization error values obtained from each of the operation modes. However, the conventional equalizer is problematic in that equalization speed decreases since the coefficient of the filter tap corresponding to the multi-path as well as the coefficients of all the filter taps are updated.